Work vehicles, such as a motor grader, can be used in construction and maintenance for creating a flat surface. When paving a road, a motor grader can be used to prepare a base foundation to create a wide flat surface for asphalt to be placed on. A motor grader can include two or more axles, with an engine and cab disposed above the axles at the rear end of the vehicle and another axle disposed at the front end of the vehicle. A blade is attached to the vehicle between the front axle and rear axle.
Motorgraders include a drawbar assembly attached near the nose of the grader which is pulled by the grader as it moves forward. The drawbar rotatably supports a circle drive member at a free end of the drawbar and the circle drive member supports a work implement such as the blade. The angle of the work implement beneath the drawbar can be adjusted by the rotation of the circle drive member relative to the drawbar assembly.
In some conventional motorgraders, the circle drive members are supported by a series of bearings attached to the drawbar and the circle drive member includes a series of gear teeth disposed to the exterior circle member or disposed to the interior of the circle member. These gear teeth cooperate with one or more drive gears associated with drive motors attached to the drawbar. In other conventional motorgraders, a worm driven gear box can be mounted to a draft frame of the grader and which rotates pinion gears which mesh with the large ring gear of the circle drive member.
In conventional motor graders, the use of a gear box has limitations. For instance, the gear box can be inefficient and thereby limiting the amount of available power to the drive the work implement. Some alternative solutions have incorporated a hydraulic cylinder, which is more efficient than the gear box. The use of multiple hydraulic cylinders, however, has limitations as well since the cylinders can only rotate the circle so far before the cylinders either crossover one another or cannot continue rotation. Occasionally, the cylinders are not operating in optimal positions and thus need to be repositioned during operation to achieve their full mechanical advantage over the conventional gear box arrangement.
Therefore, a need exists for a circle drive assembly of a motor grader to be driven by hydraulic cylinders. In addition, a need exists for the capability of repositioning the hydraulic cylinders to achieve the full 360° rotation of the circle drive assembly.